Injection molding machines characteristically mount at least two die parts. One die part is mounted to the machine frame, and the other part is mounted to a slide or carriage to close and to open the mold. The classical construction also includes knockout bars to contact a completed part to eject the part from the mold. These can more properly be regarded as ejector pins, and to avoid confusion in this specification they will be described as ejector pins, rather than as knockout bars. These ejector pins are not the pins which are the subject of this invention.
Classical molding machines also include a plate called a knockout plate. This is a very substantial rigid plate which floats relative to the movable mold part in order to actuate the ejector pins.
However, the linkage between the knockout plate and the ejector pins is not a direct one. Instead the ejector pins are mounted to still another plate, which in turn is contacted by knockout bars carried by the knockout plate.
The arrangement of the ejector pins is arbitrary, and is dictated by the configuration of the individual mold. However, the knockout bars which cause the ejector pins to eject the product are located on an array defined by a national standard. This is standard defines where the knockout bars can be mounted. It is not usual for all of these locations to carry a knockout bar at the same time. Instead, again depending on the mold characteristics, perhaps only a central pin will be used, or some pattern of two, three or more of them will be placed at proper locations in the pattern.
The point is that each time a mold is changed, it is likely that the pattern of knockout bars will also have to be changed. It Is usual for the knockout bar to be held to one side of the knockout plate by a headed bolt passed through a hole in the plate and threaded into the knockout bar. This does not appear to be a particular problem, except to the person who must remove and replace the knockout bars. He regards this as a difficult and onerous task. The knockout plate is not removed from the machine for the purpose, and access to the regions where the job is done is very restricted. The worker must work from the side reaching into a narrow region with a wrench of substantial size, often nearly blindly.
It is an object of this invention to provide mounting means which can conveniently be manipulated from outside of this narrow region, preferably by energizing a fluid motor, so that the task is reduced to merely to pulling knockout bars out of sockets where they are not needed, plugging knockout bars into sockets where they are needed, and then actuating a latch to hold them in the socket or sockets.
This arrangement eliminates the inconveniences and delays of the prior art, and enables the knockout bar array to be changed in a matter of only a few minutes instead of the hour or more required for most known machines.